1. Field of the Invention
The present invention relates to method and apparatus for assembling balls forming a ball spline of a toroidal-type continuously variable transmission, and such method and apparatus are used to facilitate the assembling operation of a toroidal-type continuously variable transmission as a transmission unit for a transmission for a car or a transmission for various kinds of industrial machines.
2. Description of the Related Art
Conventionally, as a transmission unit for a transmission for a car, it has been studied to use such a toroidal-type continuously variable transmission as schematically shown in FIGS. 12 and 13. In this toroidal-type continuously variable transmission, for example, as disclosed in JP-A-62-71465U, an input side disk 2 (a power transmission disk) is supported concentrically with an input shaft 1 (a rotary shaft), while an output side disk 4 (a power transmission disk) is fixed to the end portion of an output shaft 3 (a rotary shaft) which is disposed concentrically with the input shaft 1. In the interior portion of a casing in which the toroidal-type continuously variable transmission is stored, there are disposed trunnions 6, 6 which can be respectively swung about their associated pivot shafts 5, 5 arranged at positions along an imaginary plane that is perpendicular to an imaginary line connecting the respective axes of the input and output shafts 1 and 3, and distanced from the intersection of the imaginary plane and imaginary line, as shown in FIG. 12. This physical relation is hereinafter referred to as xe2x80x9ctorsional relation (torsional position)xe2x80x9d.
That is, these trunnions 6, 6 are structured such that the pivot shafts 5, 5 are disposed on the outer surfaces of their respective two end portions. Also, in the middle portions of the respective trunnions 6, 6, there are supported the base end portions of displacement shafts 7, 7 in such a manner that the inclination angles of the displacement shafts 7, 7 can be freely adjusted by swinging the trunnions 6, 6 about the pivot shafts 5, 5. In the peripheries of the respective displacement shafts 7, 7, there are rotatably supported power rollers 8, 8, respectively. And, these power rollers 8, 8 are held by and between the mutually opposing inner surfaces 2a, 4a of the input side and output side disks 2, 4. Each of the inner surfaces 2a, 4a is formed such that its cross section is formed as a concave surface which can be obtained by rotating an arc about its associated pivot shaft 5. Also, the power rollers 8, 8 respectively include peripheral surfaces 8a, 8a each of which is formed as a spherical-shaped convex surface, while the peripheral surfaces 8a, 8a are respectively contacted with the inner surfaces 2a, 4a. 
Between the input shaft 1 and input side disk 2, there is interposed a pressing device 9 of a loading cam type, while the input side disk 2 can be elastically pressed toward the output side disk 4 by the pressing device 9. The pressing device 9 is composed of a cam plate 10 rotatable together with the input shaft 1 and a plurality of (for example, four) rollers 12, 12 which are rollably held by a retainer 11. On one side surface (in FIGS. 12 and 13, on the left side surface) of the cam plate 10, there is formed a cam surface 13 which is a curved surface extending in the circumferential direction of the cam plate 10; and, on the outer side surface (in FIGS. 12 and 13, on the right side surface) of the input side disk 2 as well, there is formed a similar cam surface 14. And, the plurality of rollers 12, 12 are respectively supported in such a manner that they can be rotated about axes respectively extending radially with respect to the input shaft 1.
When the above-structured toroidal-type continuously variable transmission is in use, in case where the cam plate 10 is rotated in response to the rotation of the input shaft 1, the cam surface 13 presses the plurality of rollers 12, 12 against the cam surface 14 formed on the outer side surface of the input side disk 2. As a result of this, the input side disk 2 is pressed by the plurality of power rollers 8, 8 and, at the same time, in accordance with the mutually pressing actions between the pair of cam surfaces 13, 14 and the plurality of rollers 12, 12, the input side disk 2 is rotated. And, the rotational movement of the input side disk 2 is transmitted through the plurality of power rollers 8, 8 to the output side disk 4, so that the output shaft 3 fixed to the output side disk 4 is rotated.
Referring here to cases where a rotation speed ratio (a transmission ratio) between the input shaft 1 and output shaft 3 is changed, at first, in case where the rotation speed ratio is decreased between the input shaft 1 and output shaft 3, the trunnions 6, 6 may be respectively swung in a given direction about their associated pivot shafts 5, 5. And, the displacement shafts 7, 7 may be respectively inclined so that the peripheral surfaces 8a, 8a of the power rollers 8, 8, as shown in FIG. 12, can be respectively contacted with the near-to-center portion of the inner surface 2a of the input side disk 2 and the near-to-outer-periphery portion of the inner surface 4a of the output side disk 4. On the other hand, in case where the rotation speed ratio is increased between the input shaft 1 and output shaft 3, the trunnions 6, 6 may be respectively swung in the opposite direction about their associated pivot shafts 5, 5. And, the displacement shafts 7, 7 may be respectively inclined so that the peripheral surfaces 8a, 8a of the power rollers 8, 8, as shown in FIG. 13, can be respectively contacted with the near-to-outer-periphery portion of the inner surface 2a of the input side disk 2 and the near-to-center portion of the inner surface 4a of the output side disk 4. Also, in case where the inclination angles of the displacement shafts 7, 7 are set at the intermediate angles between the angles shown in FIGS. 12 and 13, there can be obtained an intermediate rotation speed ratio between the input shaft 1 and output shaft 3.
Also, FIGS. 14 and 15 show a more specified example of a conventional toroidal-type continuously variable transmission which is disclosed in JP-A-1-173552U. In the present conventional toroidal-type continuously variable transmission, an input side disk 2 and an output side disk 4 are respectively supported on the periphery of a circularpipe-shaped input shaft 15 in such a manner that they can be rotated and shifted in the axial direction of the input shaft 15 through needle roller bearings 16, 16. Also, a cam plate 10 is spline engaged with the outer peripheral surface of the end portion (in FIG. 14, the left end portion) of the input shaft 15, so that a collar portion 17 can prevent the cam plate 10 from moving in a direction to part away from the input side disk 2. And, the cam plate 10 and rollers 12, 12 cooperate together in forming a pressing device 9 of a loading cam type which, based on the rotational movement of the input shaft 15, can press and rotate the input side disk 2 toward the output side disk 4. An output gear 18 is connected to the output side disk 4 through keys 19, 19, so that the output side disk 4 and output gear 18 can be rotated in synchronization with each other.
The respective two end portions of a pair of trunnions 6, 6 are supported on a pair of support plates 20, 20 in such a manner that they can be swung and shifted in the axial direction thereof (in FIG. 14, in the front and back direction; and, in FIG. 15, in the right and left direction). And, displacement shafts 7, 7 are respectively supported on circular holes 23, 23 portions which are formed in the middle portions of the respective trunnions 6, 6. These displacement shafts 7, 7 respectively include support shaft portions 21, 21 and pivot shaft portions 22, 22 which are arranged in parallel to each other and are shifted in the axes from each other in the axes thereof. Of these support shaft portions, the support shaft portions 21, 21 are rotatably supported on the interior portions of the respective circular holes 23, 23 through their associated radial needle roller bearings 24, 24. On the other hand, on the peripheries of the respective pivot shaft portions 22, 22, there are rotatably supported power rollers 8, 8 through another radial needle roller bearings 25, 25.
By the way, the pair of displacement shafts 7, 7 are respectively disposed at the 180xc2x0 opposite positions with respect to the input shaft 15. Also, directions in which the pivot shaft portions 22, 22 of these displacement shafts 7, 7 are respectively shifted with respect to the support shaft portions 21, 21 are the same (in FIG. 15, the reversed right and left direction) with respect to the rotational direction of the input side and output side disks 2, 4. And, this shifting direction is set to be almost perpendicular to a direction where the input shaft 15 is disposed. Therefore, the power rollers 8, 8 are supported in such a manner that they can be shifted slightly with respect to the arranging direction of the input shaft 15. As a result of this, even in case where the power rollers 8, 8 tend to shift in the axial direction of the input shaft 15 (in FIG. 14, in the right and left direction; and, in FIG. 15, in the front and back direction) due to the elastic deformation of the component members of the present toroidal-type continuously variable transmission caused by large loads are applied to the component members during transmission of the rotational force, such shifts of the power rollers 8, 8 can be absorbed without applying excessive forces to the component members.
Also, between the outer surfaces of the respective power rollers 8, 8 and the inner surfaces of the middle portions of the respective trunnions 6, 6, there are disposed thrust ball bearings 26, 26 and thrust needle roller bearings 27, 27 in order starting from the outer surfaces of the power rollers 8, 8. Of these bearings, the thrust ball bearings 26, 26 respectively support the thrust-direction loads applied to their associated power rollers 8, 8 and also allow their associated power rollers 8, 8 to rotate. Also, the thrust needle roller bearings 27, 27 respectively support the thrust-direction loads applied to their associated outer races 30, 30 respectively forming the thrust ball bearings 26, 26 and also allow the pivot shaft portions 22, 22 and outer races 30, 30 to swing about their associated support shaft portions 21, 21.
Further, to the one-end portions (in FIG. 15, the left end portions) of the respective trunnions 6, 6, there are respectively connected their associated drive rods 36, 36; and, to the outer peripheral surfaces of the middle portions of the respective drive rods 36, 36, there are fixedly secured drive pistons 37, 37. And, these drive pistons 37, 37 are respectively fitted into their associated drive cylinders 38, 38 in an oil tight manner.
In the case of the above-structured toroidal-type continuously variable transmission, the rotation power of the input shaft 15 is transmitted through the pressing device 9 to the input side disk 2. And, the rotational movement of the input side disk 2 is transmitted through the pair of power rollers 8, 8 to the output side disk 4 and, further, the rotational movement of the output side disk 4 is taken out from the output gear 18. To change the rotation speed ratio between the input shaft 15 and output gear 18, the pair of drive pistons 37, 37 may be shifted in the mutually opposite directions. Due to the shifting movements of these drive pistons 37, 37, the pair of trunnions 6, 6 are respectively shifted in the mutually opposite directions, so that, for example, the power roller 8 disposed in a lower stage in FIG. 15 is shifted to the right, whereas the power roller 8 disposed in an upper stage in FIG. 15 is shifted to the left. This changes the direction of a tangential-direction force which acts on the contact portions between the peripheral surfaces 8a, 8a of the respective power rollers 8, 8 and the inner surfaces 2a, 4a of the input side and output side disks 2, 4. And, as a result of this change in the direction of the force, the respective trunnions 6, 6 are swung in the mutually opposite directions about their associated pivot shafts 5, 5 which are pivotally supported on the support plates 20, 20. As a results, as previously shown in FIGS. 12 and 13, the contact positions between the peripheral surfaces 8a, 8a of the respective power rollers 8, 8 and the inner surfaces 2a, 4a of the input side and output side disks 2, 4 are changed, thereby changing the rotation speed ratio between the input shaft 15 and output gear 18.
By the way, when the rotational force is transmitted between the input shaft 15 and output gear 18 in this manner, due to the elastic deformation of the component members of the toroidal-type continuously variable transmission, the power rollers 8, 8 are respectively shifted in the axial direction of the input shaft 15 and thus the displacement shafts 7, 7 pivotally supporting the power rollers 8, 8 are slightly rotated about the support shaft portions 21, 21. As a result of the rotational movements of the displacement shafts 7, 7, the outer surfaces of the outer races 30, 30 of the thrust ball bearings 26, 26 and the inner surfaces of the trunnions 6, 6 are caused to shift with respect to each other. Because the thrust needle roller bearings 27, 27 are present between these outer and inner surfaces, this relative shifting motion requires only a small force. Therefore, to change the inclination angles of the displacement shafts 7, 7 in the above-mentioned manner requires only a small force.
Further, for the purpose of increasing the torque that can be transmitted, as shown in FIGS. 16 and 17, conventionally, there are also known structures in which input side disks 2A, 2B and output side disks 4, 4 respectively serving as power transmission disks are disposed by twos on the periphery of an input shaft 15 which is a rotary shaft; and, the two input side disks 2A, 2B and two output side disks 4, 4 are arranged in parallel to each other with respect to the direction of transmission of the power. In each of the structures shown in FIGS. 16 and 17, an output gear 18a is supported on the periphery of the middle portion of the input shaft 15 in such a manner that it can be rotated with respect to the input shaft 15, while the output side disks 4, 4 are respectively spline engaged with the two end portions of a cylindrical portion provided on the central portion of the output gear 18. And, between the inner peripheral surfaces of the output side disks 4, 4 and the outer peripheral surfaces of the input shaft 15, there are interposed needle roller bearings 16, 16; and, the output side disks 4, 4 are respectively supported on the periphery of the input shaft 15 in such a manner that they can be rotated with respect to the input shaft 15 as well as can be shifted in the axial direction of the input shaft 15. Also, the input side disks 2A, 2B are respectively supported on the two end portions of the input shaft 15 in such a manner that they can be rotated together with the input shaft 15.
However, one (in FIGS. 16 and 17, the left side) input side disk 2A is disposed such that its back surface (in FIGS. 16 and 17, the left side surface) is butted against a loading nut 39 directly (in the case of the structure shown in FIG. 17) or through a coned disk spring 45 having large elasticity (in the case of the structure shown in FIG. 16), whereby the input side disk 2A is substantially prevented from shifting in its axial direction (in FIGS. 16 and 17, in the right and left direction) with respect to the input shaft 15. On the other hand, the input side disk 2B disposed opposed to the cam plate 10 is supported on the input shaft 15 through a ball spline 40 in such a manner that it can be shifted in its axial direction. And, between the back surface (in FIGS. 16 and 17, the right surface) of the input side disk 2B and the front surface (in FIGS. 16 and 17, the left surface) of the cam plate 10, there are interposed a coned disk spring 41 and a thrust needle roller bearing 42 in such a manner that they are arranged in series with each other. Of the two component members, the coned disk spring 41 is used to apply a preload to the contact portions between the inner surfaces 2a, 4a of the disks 2A, 2B and the peripheral surfaces 8a, 8a of the power rollers 8, 8. On the other hand, the thrust needle roller bearings 42, when the pressing device 9 is in operation, allows the input side disk 2B and cam plate 10 to rotate with respect to each other.
Also, in the case of the structure shown in FIG. 16, the output gear 18a is rotatably supported on a partition wall 44 provided in the interior portion of the housing by a pair of angular type ball bearings 43, 43, whereas the output gear 18a is prevented from shifting in the axial direction thereof. On the other hand, in the structure shown in FIG. 17, the output gear 18a is free to shift in the axial direction thereof. By the way, as shown in FIGS. 16 and 17, the reason why, in the toroidal-type continuously variable transmission of a so called double cavity type that the input side disks 2A, 2B and output side disks 4, 4 are disposed by twos in parallel to each other with respect to the power transmission direction, one or both of the input side disks 2A, 2B facing the cam plate 10 is or are supported on the input shaft 15 by the ball splines 40, 40a in such a manner as to be shifted in the axial direction thereof is to fulfill the following functions (1) and (2):
(1) the rotational movements of these two disks 2A, 2B are synchronized with each other perfectly; and,
(2) in addition to the above function (1), the two disks 2A, 2B are allowed to shift in the axial direction thereof with respect to the input shaft 15 in accordance with the elastic deformation of the component members of the toroidal-type continuously variable transmission caused by the operation of the pressing device 9.
The ball splines 40, 40a, which are disposed for the above purpose, respectively include outside diameter side ball spline grooves 46, 46 formed in the axial direction thereof at a plurality of circumferential-direction positions on the outer peripheral surface of the middle portion of the input shaft 15, inside diameter side ball spline grooves 47, 47 formed in the axial direction thereof at positions facing the outside diameter side ball spline grooves 46, 46 on the inner peripheral surfaces of the input side disks 2A, 2B, and a plurality of balls 48, 48 rollably interposed between these two kinds of ball spline grooves 46, 47. Also, in the case of the ball spline 40 which is used to support the input side disk 2B positioned on the pressing device 9 side, a securing ring 50 is secured to a securing groove 49 formed in the near-to-inner-surface 2a portion of the inner peripheral surface of the input side disk 2B, thereby preventing the plurality of balls 48, 48 from shifting toward the inner surface 2a of the input side disk 2B. And, the balls 48, 48 are thereby prevented from slipping out from between the two kinds of inner and outer diameter side ball spline grooves 46, 47. By the way, in the structure of FIG. 16, in the case of the ball spline 40a for supporting the input side disk 2A situated far from the pressing device 9, a securing ring 50a is secured to a securing groove 49a formed in the outer peripheral surface of the middle portion of the input shaft 15, thereby preventing the plurality of balls 48, 48 from shifting toward the inner surface 2a of the input side disk 2A.
Also, in JP-A-11-51135, there is disclosed a structure in which there are eliminated troubles in securing securing rings 50a, 50a to the above-mentioned securing grooves 49, 49 to thereby be able to reduce the manufacturing cost of a toroidal-type continuously variable transmission. FIGS. 18 to 22 respectively show the main portions of the toroidal-type continuously variable transmission that is disclosed in this publication. In this toroidal-type continuously variable transmission, on the outer peripheral surface of the middle portion of the input shaft 15, in more particular, on the portion of the present outer peripheral surface between the input side disk 2B and the output side disk 4 to which the input side disk 2B is opposed, there is formed a small-diameter portion 51 over the whole periphery thereof. A level difference h (see FIG. 19), which exists between the outer peripheral surface of the small-diameter portion 51 and the portion of the outer peripheral surface of the input shaft 15 that is deviated from the small-diameter portion 51, is set larger than the diameter-direction width W50 of the securing ring 50 (h greater than W50). By the way, the securing ring 50 is formed of elastic material such as stainless spring steel or synthetic resin having oil resistance and heat resistance in a partially cutaway ring shape and is provided with elasticity in a direction to spread the diameter thereof in a free state.
On the other hand, in the portion of the inner peripheral surface of the input side disk 2B that is situated near to the inner surface 2a (in FIGS. 18 to 22, near to the left side) of the input side disk 2B, there is formed a securing groove 49 over the whole periphery thereof in such a manner that it crosses perpendicularly inside diameter side ball spline grooves 46, 46 respectively formed in the inner peripheral surface of the input side disk 2B. The securing ring 50 is mounted into the securing groove 49 through the small-diameter portion 51 in such a manner that the inside diameter side opening of the securing groove 49 and the small-diameter portion 51 are matched to each other. Also, in the portion of the outer peripheral surface of the middle portion of the input shaft 15 that is situated on the opposite side end portion of the outside diameter side ball spline grooves 46, 46 with respect to the small-diameter portion 51, there is formed a securing groove 49a; and, a securing ring 50a is mounted into this securing groove 49a. The securing ring 50a, oppositely to the securing ring 50, has elasticity in a direction to shorten the outside diameter thereof in a free state. And, the securing ring 50a has a function to prevent the plurality of balls 48, 48 from slipping out toward the outer surface (in FIGS. 18 to 22, the right side surface) of the input side disk 2B.
In the case of the above-structured toroidal-type continuously variable transmission, after the input side disk 2B is fitted with the outer surface of the input shaft 15, there can be carried out an operation to insert the plurality of balls 1548, 48 forming the ball spline 40 into between the outside and inside diameter side ball spline grooves 46, 47, and an operation to mount the securing ring 50 onto the inner peripheral surface of the input side disk 2B. That is, an operation to assemble the above-mentioned structure is executed in the following manner. By the way, this assembling operation is carried out with the inner surface 2a of the input side disk 2B facing upward. This is preferable because gravity acts in a direction to calm down the component members of the toroidal-type continuously variable transmission.
In the securing groove 49a formed in the outer peripheral surface of the middle portion of the input shaft 15, there has been previously mounted the securing ring 50a. In this state, there is no possibility that the outer peripheral edge of the securing ring 50a can project out from the outer peripheral surface of the input shaft 15. Then, the component members of the pressing device 9 and input side disk 2B are fitted with the outer peripheral surface of the input shaft 15. At the then time, the securing ring 50 is not yet mounted on the input side disk 2B. And, in a state where the input side disk 2B is fitted with the outer peripheral surface of the input shaft 15 and the outside and inside diameter side ball spline grooves 46, 47 are matched to each other, the plurality of balls 48, 48 are inserted into between the outside and inside diameter side ball spline grooves 46, 47.
Next, as shown in FIG. 20, the input side disk 2B is moved in the axial direction of the input shaft 15 and the inside diameter side opening of the securing groove 49 is opened to the small-diameter portion 51. And, the securing ring 50 is fitted through the small-diameter portion 51 into the portion of the input side disk 2B that is situated near to the inner surface of the inner peripheral surface of the input side disk 2B, and the securing ring 50 is matched to the securing groove 49. Due to the elasticity of the securing ring 50 itself, as shown in FIG. 21, the securing ring 50 is engaged with the securing groove 49. By the way, when mounting the securing ring 50 into the securing groove 49 in this manner, the balls 48, 48 in contact with the securing ring 50a must be prevented from being exposed from the outer surface of the input side disk 2B, or, even when the balls are exposed, they must be exposed less than half of the diameter thereof. The reason for this consideration is that, in the mounting operation of the securing ring 50, the balls 48, 48 can be prevented from slipping out from the outer surface of the input side disk 2B.
After the securing ring 50 is mounted into the securing groove 49 in the above-mentioned manner, as shown in FIG. 22, the input side disk 2B is returned to the opposite side of the axial direction of the input shaft 15. Due to this, the securing groove 49 is shifted from the small-diameter portion 51 and the securing ring 50 is thereby prevented from slipping out from the securing groove 49. In the case of the toroidal-type continuously variable transmission that is structured and operates in the above-mentioned manner, there is eliminated the need for extra operations such as an operation to adhere the plurality of balls 48, 48 to the outside diameter side ball spline grooves 47, 47, which can facilitate the assembling operation of the toroidal-type continuously variable transmission.
However, in the case of the structure disclosed in the above-mentioned publication JP-A-11-51135, although the assembling operation of the balls 48, 48 can be facilitated, automation of this assembling operation has not been taken into consideration yet. Also, actually, in order to be able to assemble the structure disclosed in the above-mentioned publication by an automation device, in case where the balls 48, 48 are to be assembled between the two ball spline grooves 46, 47, special attention should be paid to the following point. That is, to assemble the balls 48, 48 between the two ball spline grooves 46, 47, the balls 48, 48 are inserted into cylindrical-shaped spaces respectively defined by and between the two ball spline grooves 46, 47 through openings formed in the respective one-end portions of these cylindrical-shaped spaces. However, since the diameters of these cylindrical-shaped spaces are substantially equal to or slightly larger than the diameter of the balls 48, the rolling surfaces of the balls 48, 48 inserted in the above manner are easy to be frictionally engaged with the two ball spline grooves 46, 47. Due to such frictional engagement, there is a possibility that the balls 48, 48 cannot be fed up to the deep portions of the cylindrical-shaped spaces, which makes it impossible to carry out the mounting operation of the balls 48, 48 and securing ring 50. Therefore, it is desired to provide means which is positively able to feed the balls 48, 48 up to the deep portions of the cylindrical-shaped spaces even in case where the above frictional engagement is easy to occur.
On the other hand, in JP-A-7-164264, there is disclosed an invention relating to an apparatus for automatically assembling a ball spline. However, in the case of the assembling apparatus disclosed in this publication, before an outside member including an inside diameter side ball spline groove formed in the inner peripheral surface thereof is fitted with the outer surface of a shaft member including an outside diameter side ball spline groove formed in the outer peripheral surface thereof, a plurality of balls are previously secured to the present outside diameter side ball spline groove. Due to this, the mechanism of the assembling apparatus is complicated, which makes it difficult to put the assembling apparatus into actual operation (enforcement).
The present invention aims at eliminating the above drawbacks found in the conventional methods and apparatus for assembling balls forming the ball spline of a toroidal-type continuously variable transmission. Accordingly, it is an object of the invention to provide method and apparatus for assembling balls forming the ball spline of a toroidal-type continuously variable transmission which are surely able to facilitate the assembling operation of balls forming the ball spline of a toroidal-type continuously variable transmission.
In attaining the above object, according to the invention, there are provided method and apparatus for assembling balls forming a ball spline of a toroidal-type continuously variable transmission, in which, for assembly of a ball spline through which a power transmission disk can be supported on the periphery of the middle portion of a rotary shaft forming a toroidal-type continuously variable transmission in such a manner that the power transmission disk can be shifted with respect to the rotary shaft only in the axial direction thereof, a plurality of balls forming the ball spline are supplied and assembled between each of a plurality of outside diameter side ball spline grooves respectively formed at a plurality of circumferential-direction portions of the outer peripheral surface of the middle portion of the rotary shaft in the axial direction thereof and each of a plurality of inside diameter side ball spline grooves respectively formed at a plurality of circumferential-direction portions of the inner peripheral surface of the power transmission disk in the axial direction thereof so as to face the outside diameter side ball spline grooves.
Of the above-mentioned method and apparatus for assembling balls forming a ball spline of a toroidal-type continuously variable transmission according to the invention, in the method according to one aspect of the invention, in a state where the rotary shaft is disposed in the vertical direction, the power transmission disk is disposed on the periphery of the middle portion of the rotary shaft, and the outside diameter ball spline grooves and the inside diameter ball spline grooves are matched in phase to each other. Also, there is assembled a member which is used to prevent the balls from slipping out from the lower end openings of a plurality of cylindrical-shaped spaces respectively defined by and between the outside diameter side and inside diameter side ball spline grooves. And, in this state, after the balls are supplied by a given number into each of the cylindrical-shaped spaces through the upper end openings of the cylindrical-shaped spaces, the rotary shaft and power transmission disk are shifted reciprocatingly with respect to each other in at least one direction of the circumferential direction thereof and the axial direction thereof to thereby feed the given number of balls into the lower portion of each of the cylindrical-shaped spaces.
Also, the apparatus according to a second aspect of the invention includes: a first support member for supporting the rotary shaft in a state where the rotary shaft is disposed in the vertical direction; a second support member for supporting the power transmission disk in a state where the power transmission disk is disposed on the periphery of the middle portion of the rotary shaft; a vertically shifting unit for shifting one of the first and second support members in the vertical direction; a phase matching unit for matching the phases of the inside diameter side and outside diameter side ball spline grooves to each other and also for maintaining such phase matched state; a ball supply unit for supplying the balls by a given number into each of a plurality of cylindricalshaped spaces respectively defined by and between the outside diameter side and inside diameter side ball spline grooves through the upper end openings of the cylindrical-shaped spaces; and, a swing unit for shifting at least one of the rotary shaft and power transmission disk reciprocatingly with respect to each other in the circumferential direction thereof.
As described above, in the case of the method and apparatus for assembling balls forming a ball spline of a toroidal-type continuously variable transmission according to the invention, when carrying out the ball assembling operation, in a state where the rotary shaft and power transmission disk are disposed in the vertical direction, after the balls are supplied into the cylindrical-shaped spaces respectively defined by and between the outside diameter side and inside diameter side ball spline grooves through the upper end openings of these cylindrical-shaped spaces, the rotary shaft and power transmission disk are shifted reciprocatingly with respect to each other in at least one direction of the circumferential direction thereof and the axial direction thereof. Due to this operation, there is prevented a possibility that, between the surfaces of the balls and the inner surfaces of the outside diameter side and inside diameter side ball spline grooves, there can remain such frictional forces as can prevent the balls from moving downwardly. As a result of this, due to the gravity that acts on these balls, these balls are fed into the lower portions (deep portions) of the respective cylindrical-shaped spaces. In this manner, in the case of the invention, in spite of the fact that the surfaces of the balls and the inner surfaces of the outside diameter side and inside diameter side ball spline grooves can be frictionally engaged with each other easily, there can be prevented an inconvenience that the balls can be caused to stop in the intermediate portions of the cylindrical-shaped spaces (that is, the balls are prevented from being fed into the deep portions of the cylindrical-shaped spaces). Thanks to this, the balls can be positively assembled into the respective cylindrical-shaped spaces. Also, of the aspects of the invention, according to the ball assembling apparatus as set forth in the second aspect of the invention, the above-mentioned ball assembling operation can be executed automatically. This eliminates a troublesome operation supplying the plurality of balls through the upper end openings of the respective cylindrical-shaped spaces. Also, the mechanism of the present ball assembling apparatus does not become complicated but can be made compact, which makes it possible to facilitate the incorporation of the present ball assembling apparatus into the manufacturing line of a toroidal-type continuously variable transmission.